In a machine for making or processing rolled web products, high-bulk rolled web products can adversely affect a cycle-rate capability of the machine. For instance, as roll bulks increase, rolled web product sheet counts, conversion process efficiencies, and a general throughput capability of the machine correspondingly decrease. Ironically, these decreases demand increased cycle-rates.
Improvements in machine cycle-rates are hampered in one respect by a conventional core production process. Cores are produced, for instance, to wind up the rolled web products. However, cutter assemblies used to cut the cores to specific sizes have reached the limits of known technology. The typical cutter assembly uses saw blades and slitters that limit core production speed and efficiency and thus limit machine cycle-rates.
A core is usually formed on a winding mandrel from unwind stations known as “unwinds”. The core is often made of paper, paperboard, cardboard, and other windable materials. The unwinds unwind webs of the windable material onto a winding mandrel to form the core. Typically, glue is applied to one or more webs of the windable material, which are helically wound by a winding mandrel to form a continuous core. A downstream cutter assembly cuts the continuous core to specific lengths.
One type of a cutter assembly is known to include a knife or saw blade disposed on a track assembly. The saw blade is positioned on the track assembly to directly contact the continuous core. The core is cut as the saw blade is moved across a circumferential surface of the core. A problem with this type of mechanical cutter assembly is that the saw blade becomes worn and dull over time. In addition to forming undesirable paper lint and dust, a dull saw blade eventually causes the core to be torn apart, rather than to be cut cleanly.
Torn cores also occur when the saw blade lags behind or does not match the speed of the core. A drop in saw blade speed could occur due to a drop in air pressure in a mill or due to mechanical problems associated with bearings and cam followers in known cutter assemblies. Moreover, torn cores result from faulty glue application during the core winding stage. Faulty glue application is caused by insufficient application of glue, missed areas in the overlap area of the windable material, and/or inconsistent glue absorption of the windable material. A water drop or absorption rate of the windable material, or a change in the glue viscosity can render the glue at least partially ineffective. When the dull saw blade catches an ineffective glue seam in the overlap area, the core is torn and edges of the glued core are “kicked up.”
Torn cores exhibit what are termed in the industry as “pulled ears,” tails, or flags. Whether caused by mechanical problems associated with conventional cutter assemblies, or due to faulty glue applications, pulled ears cause significant problems in a downstream machine direction. For instance, as a core is rotating at high speed and begins to wind up a sheet of the rolled web product, a pulled ear on the core can tear out the sheet and force a machine stoppage.
In an effort to prevent pulled ears, large amounts of glue are now applied to entire surfaces of the windable material before the material is wound on the winding mandrel. This approach may prevent some pulled ears but it uses more glue than is desirable. Excessive glue application is costly and creates clean-up problems in the winding mandrel and further downstream.
A cutter assembly for cutting cores that is not susceptible to mechanical wear at the cutting point, which does not require machine downtime to clean up excess glue, and which results in a relatively smooth cut edge that is free of lint, dust, and pulled ears is needed.